Which term is defined in Rule 3?

Answer: B — Vessel

Rule 3 of the COLREGs provides essential definitions that clarify the terms used throughout these regulations. The term "vessel" is defined in this rule to encompass a broad range of watercraft operating on navigable waters, ensuring that all vessels, regardless of type or size, are subject to the same navigational rules. This definition is foundational because it allows for the uniform application of the rules to various types of marine vessels, including commercial ships, recreational boats, barges, and more. The other terms listed, such as "anchor," "skipper," and "port," may be relevant to navigation or the operation of vessels, but they do not possess specific definitions within Rule 3 itself. In contrast, defining "vessel" establishes a critical understanding necessary for applying the rules effectively and ensuring safe maritime operations.